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11.
Paul B. M. Joyce David F. Spencer Linda Bonen Michael W. Gray 《Plant molecular biology》1988,10(3):251-262
We have begun a systematic search for potential tRNA genes in wheat mtDNA, and present here the sequences of regions of the wheat mitochondrial genome that encode genes for tRNAAsp (anticodon GUC), tRNAPro (UGG), tRNATyr (GUA), and two tRNAsSer (UGA and GCU). These genes are all solitary, not immediately adjacent to other tRNA or known protein coding genes. Each of the encoded tRNAs can assume a secondary structure that conforms to the standard cloverleaf model, and that displays none of the structural aberrations peculiar to some of the corresponding mitochondrial tRNAs from other eukaryotes. The wheat mitochondrial tRNA sequences are, on average, substantially more similar to their eubacterial and chloroplast counterparts than to their homologues in fungal and animal mitochondria. However, an analysis of regions 150 nucleotides upstream and 100 nucleotides downstream of the tRNA coding regions has revealed no obvious conserved sequences that resemble the promoter and terminator motifs that regulate the expression of eubacterial and some chloroplast tRNA genes. When restriction digests of wheat mtDNA are probed with 32P-labelled wheat mitochondrial tRNAs, <20 hybridizing bands are detected, whether enzymes with 4 bp or 6 bp recognition sites are used. This suggests that the wheat mitochondrial genome, despite its large size, may carry a relatively small number of tRNA genes. 相似文献
12.
Effect of Sorbinil on myo-Inositol Metabolism in Cultured Neuroblastoma Cells Exposed to Increased Glucose Levels 总被引:6,自引:6,他引:0
Neuroblastoma cells were used to determine the effect of sorbinil on myo-inositol metabolism in cells exposed to elevated levels of glucose in culture. Exposing cells to elevated levels of glucose led to an increase in levels of intracellular sorbitol. The increase in sorbitol levels was dependent on the extracellular glucose concentration. In contrast, the myo-inositol content of cells was decreased in the presence of increasing concentrations of extracellular glucose. Increasing the concentration of glucose in the culture medium caused a decrease in myo-inositol uptake and in the incorporation of extracellular myo-inositol into phospholipid. The effect of elevated glucose levels on myo-inositol metabolism and sorbitol accumulation was blocked by addition of 0.4 mM sorbinil. The ability of sorbinil to block the decrease in myo-inositol metabolism and sorbitol accumulation caused by 30 mM extracellular glucose was dependent on its concentration. Maximal effects were obtained with 0.4 mM sorbinil. However, there was some variation in the degree of effectiveness among batches of sorbinil. These results at the cellular level suggest that the intracellular accumulation of sorbitol is responsible for the alteration of myo-inositol metabolism observed in neuroblastoma cells exposed to elevated glucose concentrations. 相似文献
13.
Vera Yip Mary Ellen Pusateri Joyce Carter Irwin A. Rose Oliver H. Lowry 《Journal of neurochemistry》1988,50(2):594-602
The distribution of glucose-1,6-bisphosphate (G16P2) synthase was measured in more than 70 regions of mouse brain, and nine layers of monkey retina. Activities in gray areas varied as much as 10-fold, in a hierarchical manner, from highest in telencephalon, especially the limbic system, to lowest in cerebellum, medulla, and spinal cord. The synthase levels were significantly correlated among different regions with G16P2 itself, as well as with previously published levels of a brain specific IMP-dependent G16P2 phosphatase. In contrast, neither G16P2 nor either its synthase or phosphatase correlated positively with phosphoglucomutase, and in all regions the G16P2 levels greatly exceeded requirements for activation of this mutase. This strengthens the view that G16P2 has some function besides serving as coenzyme for phosphoglucomutase. However, attempts to correlate the "G16P2 system," as defined by the three coordinately related elements, synthase, phosphatase, and G16P2, with other enzymes of carbohydrate metabolism, or with regional data of Sokoloff et al. [J. Neurochem. 28, 897-916 (1977)] for glucose consumption, were unsuccessful. This leaves open the possibility that brain G16P2 might serve as a phosphate donor for specific nonmetabolic effector proteins. 相似文献
14.
Effect of Increased Glucose Levels on Na+ /K+ -Pump Activity in Cultured Neuroblastoma Cells 总被引:1,自引:0,他引:1
Neuroblastoma cells were used to analyze the effect of elevated glucose levels on myo-inositol metabolism and Na+/K+-pump activity. The activity of the Na+/K+ pump in neuroblastoma cells is almost totally sensitive to ouabain inhibition. Culturing neuroblastoma cells in 30 mM glucose caused a significant decrease in Na+/K+-pump activity, myo-inositol metabolism, and myo-inositol content, compared to cells grown in the presence of 30 mM fructose. Glucose supplementation also caused a large intracellular accumulation of sorbitol. The aldose reductase inhibitor sorbinil prevented the abnormalities in myo-inositol metabolism and partially restored Na+/K+-pump activity in neuroblastoma cells cultured in the presence of elevated glucose levels. These results suggest that the accumulation of sorbitol by neuroblastoma cells exposed to elevated concentrations of extracellular glucose causes a decrease in myo-inositol metabolism and these abnormalities are associated with a reduction in Na+/K+-pump activity. 相似文献
15.
Summary Resource utilization by cutthroat trout (CT) and Dolly Varden charr (DV) was studied 8 years after experimental transfers from sympatry had established reproducing allopatric populations in two nearby fishless lakes. Allopatric DV significantly increased their utilization of shallow-dwelling zoobenthos, and increased their vertical distribution in comparison to that in sympatry. In contrast, allopatric CT showed little change in the proportions of major prey types utilized, and, if anything, restricted their vertical distribution in comparison to that in sympatry. The results can be explained by the hypothesis that the resource use of DV is strongly influenced by interspecific competition from CT, whereas CT largely remains unaffected by this interaction. An alternative hypothesis, that lake differences can explain the differences in resource use between sympatry and allopatry, was evaluated by comparing food resource availability and other biotic and abiotic characteristics of the three study lakes. None of these could account for the shift in resource use by DV between sympatry and allopatry, but lake differences may explain why allopatric CT showed a restricted habitat use in comparison with their sympatric donor stock. The results of this whole-lake transfer experiment are consistent with earlier reported field and laboratory studies, and suggest that the aggressive dominance of CT is the most important mechanism by which DV are displaced from littoral and near-surface habitats in sympathy with CT. 相似文献
16.
Summary Many stormpetrel species breed in habitats where their populations cannot be estimated by direct counts of burrows or birds; mark-recapture experiments have been confounded by the presence of many wandering non-breeders. With a population of Wilson's Stormpetrel Oceanites oceanicus at Bird Island, South Georgia, we tried to estimate the proportion of breeding females in samples obtained during a mark-recapture experiment. These were identified by measurements of the cloaca, which greatly enlarges at egg-laying. A concurrent experiment with individually marked birds determined that breeding females could be discriminated from males and non-breeders for c 30 days after laying. The technique is probably applicable to other petrels, though it will work best with those that lay most synchronously. The overall population estimate was 4841–5515 birds (SE 856–1417); estimates of breeding females gave a population of 2300 paris early in the incubation period and 1400 pairs near hatching. 相似文献
17.
J E Lindstrom R C Prince J C Clark M J Grossman T R Yeager J F Braddock E J Brown 《Applied and environmental microbiology》1991,57(9):2514-2522
The effort of clean up the T/V Exxon Valdez oil spill in Prince William Sound, Alaska, included the use of fertilizers to accelerate natural microbial degradation of stranded oil. A program to monitor various environmental parameters associated with this technique took place during the summer of 1990. Microbiological assays for numbers of heterotrophic and oil-degrading microbes and their hydrocarbon mineralization potentials were performed in support of this program. Fertilizer addition resulted in higher hexadecane and phenanthrene mineralization potentials on treated plots than on untreated reference plots. Microbial numbers in treated and reference surface sediments were not significantly different immediately after the first nutrient application in May 1990. However, subsurface sediments from treated plots had higher numbers of hydrocarbon degraders than did reference sediments shortly after treatment. The second application of fertilizer, later in summer, resulted in surface and subsurface increases in numbers of hydrocarbon degraders with respect to reference sediments at two of the three study sites. Elevated mineralization potentials, coupled with increased numbers of hydrocarbon degraders, indicated that natural hydrocarbon biodegradation was enhanced. However, these microbiological measurements alone are not sufficient to determine in situ rates of crude oil biodegradation. 相似文献
18.
Effect of microspore stage and media on anther culture of peanut (Arachis hypogaea L.) 总被引:2,自引:0,他引:2
Martha C. Willcox Sandra M. Reed Joyce A. Burns J. C. Wynne 《Plant Cell, Tissue and Organ Culture》1991,24(1):25-28
This study was designed to study the effects of stage of microspore development and culture medium on androgenic response in peanut (Arachis hypogaea L.). Anthers of various developmental stages were cultured for 7 days, then fixed and observed cytologically. Three sets of media, involving different basal media, growth regulators, sucrose levels and glutamine concentrations, were tested. In all experiments, the stage of development of the microspores at the time of culture was highly significant. The early uninucleate microspores stage was identified as producing the highest anther response rating. The effect of media was nonsignificant in all experiments. However, the stepwise modification of the media through the course of the study resulted in an almost 8 x increase in anther response rating. Numerically, the best media tested was N6 basal medium with 1 mg 1-1 NAA, 0.1 mg 1-1 BA, 5.5% sucrose, and 3.5 g 1-1 glutamine. While no haploids were obtained, four-nucleate cells were observed, indicating the potential in peanuts for an androgenic reponse. 相似文献
19.
Of 18 commercially used textile dyes, eight were degraded by the white rot fungus,Phanerochaete chrysosporium, by 40 to 73% based on decrease of colour. Both the lignin-degrading enzyme system ofP. chrysosporium and adsorption to its cell mass were involved in the degradation of the diazo dye, Reactofix Gold Yellow. Degradation was best achieved by adding the dye to the medium and then inoculating with pre-grown mycelium; inoculation with spores resulted mainly in dye adsorption. 相似文献
20.
Predictive model of conjugative plasmid transfer in the rhizosphere and phyllosphere. 总被引:4,自引:3,他引:1
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G R Knudsen M V Walter L A Porteous V J Prince J L Armstrong R J Seidler 《Applied microbiology》1988,54(2):343-347
A computer simulation model was used to predict the dynamics of survival and conjugation of Pseudomonas cepacia (carrying the transmissible recombinant plasmid R388:Tn1721) with a nonrecombinant recipient strain in simple rhizosphere and phyllosphere microcosms. Plasmid transfer rates were derived for a mass action model, and donor and recipient survival were modeled as exponential growth and decay processes or both. Rate parameters were derived from laboratory studies in which donor and recipient strains were incubated in test tubes with a peat-vermiculite solution or on excised radish or bean leaves in petri dishes. The model predicted donor, recipient, and transconjugant populations in hourly time steps. It was tested in a microcosm planted with radish seeds and inoculated with donor and recipient strains and on leaf surfaces of radish and bean plants also growing in microcosms. Bacteria were periodically enumerated on selective media over 7 to 14 days. When donor and recipient populations were 10(6) to 10(8) CFU/g (wet weight) of plant or soil, transconjugant populations of about 10(1) to 10(4) were observed after 1 day. An initial rapid increase and a subsequent decline in numbers of transconjugants in the rhizosphere and on leaf surfaces were correctly predicted. 相似文献